Class A vs Class B Multiple Dwellings Explained
You'll see "Class A" and "Class B" all over HPD rules, from detector notices to registration. They sound technical, but the difference is simple: is the building for people who live there long term, or for short stays? Here's what each class means and why it matters for your signs.
The quick answer
In short: Under the Multiple Dwelling Law Section 4, a Class A multiple dwelling is used for permanent residence, generally 30 days or more, like apartment buildings. A Class B multiple dwelling is used for transient stays, like hotels, rooming houses and lodging houses.
Class A: where people live
Most NYC residential buildings are Class A. That includes apartment houses, walk ups, garden apartments, co-ops, condos and 3 family houses. Almost everything on this blog, from the required signs checklist to CO alarm rules, is written for Class A buildings.
Class B: short stays
- 1HotelsTransient guests, usually staying less than 30 days.
- 2Rooming and lodging housesRooms rented individually, often with shared facilities.
- 3Some SROs and dormitoriesDepending on how the building is classified.
Why the class matters for signs
Hotel units and Class B rooming units need a maximum occupancy sign inside each unit (HMC Section 27-2075).
Detector notice rules are written for Class A buildings, and natural gas rules give Class B owners a central system option. See natural gas detectors.
The smoking policy law applies to Class A multiple dwellings. See Local Law 147.
FDNY fire safety notices are for residential occupancy group R-2, the typical apartment building.
Running a hotel or rooming house? Ask us about maximum occupancy signs for each room. Contact us
How to find your building's class
Check your Certificate of Occupancy, or look up the building on HPD Online, which shows the building class. If the way the building is used doesn't match its class, talk to an expediter or attorney, since that can be a bigger issue than signs.
What this looks like in practice
Say an owner has two buildings: a 20 unit walk up in Sunset Park and a small rooming house in the Bronx. The walk up gets the standard Class A set from our package guide. The rooming house also needs maximum occupancy signs in each room and its own review of which detector and fire rules apply. Same owner, two different sign lists.
Official sources: NY Multiple Dwelling Law Section 4, HPD Required Signage, HPD Online.
Quick answers
What is a Class A multiple dwelling?
A building with 3 or more units used for permanent residence, generally 30 days or more, like an apartment building.
What is a Class B multiple dwelling?
A building used for transient stays, like a hotel, rooming house or lodging house.
Where can I check my building's class?
On your Certificate of Occupancy or on HPD Online.
Not sure what your building needs?
Send us your address and number of apartments. We will tell you exactly which signs to order.
General information based on the NYC HPD Required Signage page as of November 2026. Not legal advice. HPD Signs NYC is not affiliated with the City of New York or HPD. Prices may change. Check nyc.gov/hpd for the latest rules.